SynopsisWith the objective of optimizing the process parameters of the R. H. Degassing LTnit of USIMINAS (Brazil), the circulation rates in a 1: 5.3 scale model were evaluated for various gas injection rates and dimensionless correlations were obtained at for three different experimental conditions of static water level in the upleg. In general, the circulation velocity increases with increasing the gas injection rate and it shows a maximum when the water level in the upleg reaches the barometric height. The circulation velocities calculated from energy balance were close to the experimentally observed values. Application of the results of cold model experiments to the industrial installation has been discussed.
METHODS, MATERIALS, AND EQUIPMENT Production of sinters in pilot sintering unitVarious sinter microstructures were produced in the laboratory using the same iron ore blend, Sinters with various mineralogical constituents were provarying only the sinter basicity and the carbon duced in the pilot sintering unit of Usiminas, starting with content of the blend via limestone and coke a basic sinter mix and varying the coke and CaCO 3 peradditions, respectively. The sinter cakes were centages, thereby bringing about changes in the thermal level subjected to low temperature, size degradation and basicity of the sinter. 1 1 ,1 2 In all sinters, the volume of tests and their structural composition was slag (CaO+SiO 2 ) was maintained constant by the addition determined. A relationship has been established of quartzite. The variables in the types of sinter produced between sinter structural composition and its size were determined on the basis of a study of the Fe 2 O 3 -CaOdegradation under low temperature reducing SiO 2 phase diagram and other investigations in respect conditions. Also, varying the gas composition led to of the formation of diVerent phases during the sintering development of a new reduction test procedure, process. 1 3 -1 5 which is more sensitive to microstructural Furthermore, the Al 2 O 3 and TiO 2 contents of the sinter variations than the conventional standard test were varied by additions of bauxite and ilmenite to the (reduction degradation index, RDI).I&S/1574 basic sinter mix, to study the eVect of these components on the reduction degradation behaviour of the sinters.
It is known that the presence of Al 2 O 3 and TiO 2 tends to increase the intensity of the reduction degradation of sinter. To enable a basic understanding of the phenomena taking place, the present work evaluates some aspects of paramount importance, such as: (a) microstructural changes of sinter containing Al 2 O 3 and TiO 2 during low temperature reduction; (b) theoretical and experimental volume changes occurring during the hematite to magnetite reduction step as well as the effect of Al 2 O 3 and TiO 2 in solid solution with hematite, using absolute dilatometry; and (c) crystal lattice distortions of hematite and magnetite owing to solid solution with Al 2 O 3 and TiO 2 , determined by line broadening of X-ray diffraction peaks. The results show that hematite containing Al 2 O 3 and 1 Characteristics of reduction of sinter in present-study: TiO 2 , subjected to a reduction process to the AT ambient temperature magnetite stage, yields a magnetite phase with a distorted crystal structure. This phenomenon, in association with structural deformation resulting from the volumetric expansion of hematite crystals METHODS, MATERIALS, AND EQUIPMENT during reduction, can cause crack generation and Microstructural changes in sinter during reduction propagation in the sinter, leading to disintegration. For evaluating microstructural changes in sinter during I&S/1573 reduction at low temperatures, sinters containing Al 2 O 3 and TiO 2 were produced in a pilot sintering unit. The
A kinetic model of hot-metal desulfurization by deep injection of synthetic powdermixtures is presented.The approach takes into consideration the transient contribution due to the particles dispersed in the bulk metal and those located at the bubble-metal interface, the influence of the carry-over slag as well as the volumeand composition of the top slag. Themodel has been utilized to assess the influence of the treatment temperature, rate of injection of powder mixtures, gas flow rate and initial concentration of sulphur over the desulfurization kinetics.In the second part of this study an analysis of the industrial data for injection of powdermixtures using this model is described.
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